Are human actors really necessary? Couldn't computers do the job better? Don't rag on me. These are serious questions. So far this summer, acting is nearly nonexistent. You saw The Fast and the Furious. In retaliation comes Final Fantasy: The Spirits Within, a sci-fi flick (loosely based on the PlayStation game series) that replaces humans with computer-generated images (CGIs). Eyeball that babe in the photo on this page — she's not real, she's virtual. Director Hironobu Sakaguchi, who created the games, uses actors only for their voices. So when you see the curvaceous Dr. Aki Ross (voiced by Ming-Na) trying to save our decimated planet from invading phantoms, you're seeing the handiwork of a computer, not of Mother Nature. Ever since Sony Pictures previewed Final Fantasy, online critics have been predicting doom. But the film exerts a hold. The crux is: for how long? At first it's fun to watch the characters, including a hero (Alec Baldwin), a villain (James Woods) and a feisty doctor (Donald Sutherland), hopping around inside a dome that encloses what's left of Manhattan. But then you notice a coldness in the eyes, a mechanical quality in the movements. Familiar voices emerging from the mouths of replicants erect a distance. The dark backgrounds leave you with the deadening feeling you get after too many hours of playing cybergames. You miss something. It could be the joystick, the interaction. More likely, it's the human touch from those pesky actors.